It has been known for many years to provide photographic elements, including both films and papers, with antistatic protection. Such protection is very important since the accumulation of static electrical charges on photographic elements is a very serious problem in the photographic art. These charges arise from a variety of factors during the manufacture, handling and use of photographic elements. For example, they can occur on sensitizing equipment and on slitting and spooling equipment, and can arise when the paper or film is unwound from a roll or as a result of contact with transport rollers. The generation of static is affected by the conductivity and moisture content of the photographic material and by the atmospheric conditions under which the material is handled. The degree to which protection against the adverse effects of static is needed is dependent on the nature of the particular photographic element. Thus, elements utilizing high speed emulsions have a particularly acute need for antistatic protection. Accumulation of static charges can cause irregular fog patterns in a photographic emulsion layer, and this is an especially sever problem with high speed emulsions. Static charges are also undesirable because they attract dirt to the photographic element and this can cause repellency spots, desensitization, fog and physical defects.
To overcome the adverse effects resulting from accumulation of static electrical charges, it is conventional practice to include an antistatic layer in photographic elements. Typically, such antistatic layers are composed of materials which dissipate the electrical charge by providing a conducting surface. A very wide variety of antistatic agents are known for use in antistatic layers of photographic elements. For example, U.S. Pat. No. 2,649,374 describes a photographic film comprising an antistatic layer in which the antistatic agent is the sodium salt of a condensation product of formaldehyde and naphthalene sulfonic acid. An antistatic layer comprising an alkali metal salt of a copolymer of styrene and styrylundecanoic acid is disclosed in U.S. Pat. No. 3,033,679. Photographic films having an antistatic layer containing a metal halide, such as sodium chloride or potassium chloride, as the conducting material, a polyvinyl alcohol binder, a hardener, and a matting agent are described in U.S. Pat. No. 3,437,484. In U.S. Pat. No. 3,525,621, the antistatic layer is comprised of colloidal silica and an organic antistatic agent such as an alkali metal salt of an alkylaryl polyether sulfonate, an alkali metal salt of an arylsulfonic acid, or an alkali metal salt of a polymeric carboxylic acid. Use in an antistatic layer of a combination of an anionic film forming polyelectrolyte, colloidal silica and a polyalklene oxide is disclosed in U.S. Pat. No. 3,630,740. In U.S. Pat. No. 3,655,386, the surface conductivity of photographic film is improved by coating it with an aqueous alcohol solution of sodium cellulose sulfate. In U.S. Pat. No. 3,681,070, an antistatic layer is described in which the antistatic agent is a copolymer of styrene and styrene sulfonic acid. U.S. Pat. No. 4,542,095 describes antistatic compositions comprising a binder, a nonionic surface-active polymer having polymerized alkylene oxide monomers and an alkali metal salt. In U.S. Pat. No. 4,623,594, an antistatic layer is formed by curing a composition comprising an electron radiation curable prepolymer and an electron radiation reactive antistatic agent that is soluble in the prepolymer.
It is known to prepare an antistatic layer from a composition comprising vanadium pentoxide as described, for example, in Guestaux, U.S. Pat. No. 4,203,769 issued May 20, 1980. Antistatic layers which contain vanadium pentoxide provide excellent protection against static and are highly advantageous in that they have excellent transparency and their performance is not significantly affected by changes in humidity. It is also known to provide such vanadium pentoxide antistatic layers with a protective overcoat layer that provides abrasion protection and/or enhances frictional characteristics, such as a layer of a cellulosic material.
In some types of photographic elements, the antistatic layer is located on the side of the support opposite to the image-forming layers and it is not necessary for there to be any functional layers overlying the antistatic layer, except for the optional inclusion of a protective overcoat layer. Vanadium pentoxide antistatic layers, with or without the inclusion of polymeric binders, are very effectively employed with such elements, and may serve as the outermost layer or, optionally, may be provided with an overlying cellulosic layer which serves as a protective abrasion-resistant topcoat layer. In other types of photographic elements, however, the antistatic layer must function as both a subbing layer and an antistatic layer. Thus, for example, many photographic elements utilize, on the side of the support opposite to the image-forming layers, a gelatin-containing pelloid layer which functions to control curl. With such elements, it is typical to employ a layer underlying the curl control layer which functions as both a subbing layer and an antistatic layer. Other photographic elements, such as X-ray films, are coated with silver halide emulsion layers on both sides and are provided with a layer which functions as both a subbing layer and antistatic layer underlying each silver halide emulsion layer. Serious difficulties are encountered when vanadium pentoxide antistatic layers are utilized as subbing layers. Thus, for example, silver halide emulsion layers and curl control layers do not adhere well to the vanadium pentoxide antistatic layer and, in consequence, delamination can occur. Moreover, the vanadium pentoxide can diffuse from the subbing layer through the overlying emulsion layer or curl control layer into the processing solutions and thereby result in diminution or loss of the desired antistatic protection.
It is toward the objective of providing a photographic support material, utilizing a vanadium pentoxide antistatic layer, which does not suffer from the aforesaid adhesion and diffusion problems that the present invention is directed.